The association between vitamin K2 intake and glucose homeostasis in individuals with and without chronic kidney disease

Thesis (Master's)--University of Washington, 2016-08

Background: Type 2 diabetes mellitus (T2DM) is the most common metabolic disorder worldwide. Subclinical micronutrient deficiencies have been found to contribute to glucose intolerance and insulin resistance. Vitamin K2, in particular, possesses extrahepatic activities that may influence glucose metabolism. Individuals with chronic kidney disease (CKD) have poorer vitamin K status as well as impaired insulin sensitivity and glucose tolerance. However, whether or not the poorer metabolic outcome correlates with intakes of vitamin K2 is unclear. Objective: The objective was to investigate whether the intake of vitamin K2 is associated with glucose tolerance and key factors determining glucose tolerance. Design: A cross-sectional investigation was undertaken using data from the Study of Glucose and Insulin in Renal Disease (SUGAR) study that involved individuals with (n=53) and without CKD (n=39). Three-day dietary records were used to estimate intakes of vitamin K2, using values of vitamin K2 for foods in nutrient databases and relevant publications. Intravenous-glucose-tolerance tests (IVGTT), oral glucose-tolerance test (OGTT) and hyperinsulinemic-euglycemic clamps were performed to assess glucose tolerance, β-cell function and insulin sensitivity. Results: In multivariate analyses adjusted for age, sex, BMI, race/ethnicity, eGFR and vitamin D status, higher vitamin K2 intake was associated with better glucose tolerance (P = 0.047). Higher vitamin K2 intake was also associated with insulin sensitivity (P = 0.017) in a crude model, but this association was attenuated and no longer significant after adjusting for classical risk factors. Vitamin K2 intake was not associated with β-cell function. Conclusion: Higher vitamin K2 intake was associated with better glucose tolerance.